This invention relates generally to a terminal block assembly for a leadless electric motor and, more particularly, to a multi-wire terminal block assembly which is especially well-suited for use with a mating connector assembly.
Small electric motors typically include a stator assembly having one or more windings, a rotor assembly rotatably mounted within the stator assembly, a shell or housing surrounding the stator assembly, and end bell assemblies fitted to the ends of the shell. The rotor assembly includes a rotating shaft which is supported in bearings carried by the end bell assemblies. In order to connect the windings of the stator assembly to an external source of power, it is necessary for conductors to pass through the motor shell or end bells. It is often desirable to use a terminal block assembly which is mounted in the shell of the motor housing for this purpose. The terminal block assembly typically includes a plurality of terminals which are connected by wires to the windings of the stator assembly, and which are exposed for connection to external conductors or mating terminals. Examples of terminal block assemblies of this general type are shown in U.S. Pat. Nos. 3,012,159 and 4,429.243.
Terminal block assemblies used with relatively small electric motors (such as fractional or low horsepower motors) must meet a number of important design criteria. Such terminal block assemblies must be relatively low in cost and relatively easy to install to avoid adding unduly to the cost of manufacturing the motor. These terminal block assemblies must also be sturdily constructed and capable of secure and vibration-free attachment to the motor shell. It is also desirable that such terminal block assemblies be designed to prevent the entry of dust, dirt, moisture and other contaminants into the motor.
Small electric motors which incorporate terminal block assemblies of the type described above and below are often referred to as "leadless" motors. Leadless motors are used in a variety of applications and are often installed under "field" conditions by personnel having varying levels of training and experience. Accordingly, it is desirable and advantageous to provide, in the design of the subject terminal block assemblies, a mechanism for assuring positive and reliable connection to one or more mating connector assemblies. It is also desirable and advantageous to provide features which prevent connection of a mating connector assembly to the terminal block assembly in other than a predetermined desired orientation to minimize the possibility of faults resulting from unintentional misconnections.
An object of the present invention is to provide a terminal block assembly for a leadless electric motor which is relatively inexpensive to produce and install.
Another object of the present invention is to provide a terminal block assembly which is sturdily constructed and which is resistant to vibration and loosening of its components.
Yet another object of the present invention is to provide a terminal block assembly which may be readily and securely mounted in the shell of an electric motor.
Yet another object of the present invention is to provide a terminal block assembly which incorporates a latching mechanism to provide for positive and reliable connection to a mating connector assembly.
Still another object of the present invention is to provide a terminal block assembly which prevents connection of a mating connector assembly in other than a predetermined desired orientation.
These and other objects of the invention are attained in a terminal block assembly for a leadless motor which is constructed in accordance with the present invention. A preferred embodiment of the terminal block assembly includes a housing, and means for securing the housing in an opening, such as a slot, in a shell of the motor. A plurality of spaced-apart motor leads and terminals are mounted in the housing such that the motor leads extend inwardly of the shell, and the terminals extend radially outwardly from a central axis of the motor. The preferred embodiment further includes means on the housing for receiving a mating connector assembly having a plurality of spaced-apart leads and terminals, corresponding to the motor leads and terminals mounted in the housing. The invention further includes means on the housing for receiving a latching mechanism on the mating connector assembly to releasably secure the mating connector assembly to the terminal block assembly. The preferred embodiment is further provided with means on the housing for preventing the mating connector assembly from being matingly received by the terminal block assembly in other than a predetermined desired orientation.
In a preferred embodiment, the terminal block assembly of the present invention is molded as a single piece from a flame resistant thermoplastic material, such as General Electric VALOX 310SEO or VALOX 325. The plurality of spaced-apart motor leads and terminals are preferably molded in place, rather than affixed to the housing afterward to reduce possible movement and vibration of the leads and terminals, to promote better sealing of the motor, and to otherwise enhance the unitary nature of the assembly.
The means on the terminal block housing for receiving a mating connector assembly preferably includes first and second generally horizontal opposing side walls, first and second generally vertical opposing end walls extending between respective ends of the first and second horizontal side walls, and a plurality of spaced apart, generally vertical separating walls extending between the first and second horizontal side walls to create a plurality of open box-like enclosures around the exposed ends of the plurality of motor terminals mounted in the housing. The open box-like enclosures of the terminal block assembly receive box-like extensions of the connector assembly in a mating relationship. The means on the housing for receiving a latching mechanism on the connector assembly comprises an open box-like structure formed on an exterior surface of the first horizontal side wall. The open box-like structure includes means, such as a window-like opening formed in a surface of the box-like structure, for retaining a locking edge of the locking mechanism on the connector assembly. The locking mechanism is easily disengaged by applying pressure to an extending tab to disengage the locking edge of the latching mechanism from the window of the box-like structure on the terminal block assembly.
An additional feature of the preferred embodiment of the invention includes means on the housing for preventing the mating connector assembly from being received by the terminal block assembly in other than a predetermined desired orientation. This means preferably includes a raised projection formed on an exterior surface of the second horizontal side wall, in substantially opposing relation to the open box-like structure formed on an exterior surface of the first horizontal side wall, such that the raised projection interacts with the latching mechanism of the connector assembly to prevent mating of the connector and terminal block assemblies when the connector assembly is rotated 180.degree. from the predetermined desired orientation. Additional safeguards include forming the separating walls to have substantially uniform wall thicknesses, corresponding to widths of respective mating openings on the connector assembly, and forming at least a portion of the end walls to have substantially greater wall thicknesses than the separating walls to prevent mating of the connector and terminal assemblies when the connector assembly is laterally (horizontally) offset from the predetermined desired orientation.
The means for securing the housing in the opening in the motor shell preferably comprises a plurality of radially-spaced flanges, including a fitted flange having a radius of curvature substantially equal to the radius of curvature of the motor shell, an outer flange having a radius of curvature slightly greater than the radius of curvature of the motor shell, and an inner flange having a radius of curvature slightly less than the radius of curvature of the motor shell. The fitted flange is dimensioned to fit within a slot or opening formed in an end of the motor shell such that first, second and third edges of the flange abut respective first, second and third edges of the slot. At least two of the edges of the outer and inner flanges extend along the exterior and interior surface of the motor shell, respectively, beyond the abutting edges of the fitted flange and the slot to prevent inward and outward radial movements of the housing. An end bell of the motor abuts a fourth edge of the fitted flange to trap the flange between an edge of the slot and the end bell, to prevent axial movements of the housing. In an especially preferred embodiment, a plurality of crushable projections are formed on the edge of the fitted flange which abuts the end bell of the motor, to assure that the fitted flange is securely fixed between the edges of the slot in the end bell, notwithstanding normal tolerance variations in machining the slot and end bell, or in forming the terminal block assembly.